The present invention relates to methods and apparatus for monitoring an electrical power or current consuming device, or consumer.
Methods and apparatus for monitoring electrical power or current consuming devices, or consumers, which are used in motor vehicles and especially in fuel supply systems, are known.
It is an object of the present invention to provide an improved method for monitoring an electrical power or current consuming device or consumer, especially in a motor vehicle and particularly its fuel supply system.
It is another object of the present invention to provide an improved apparatus or system for monitoring an electrical power or current consuming device or consumer, especially in a motor vehicle and particularly its fuel supply system.
In the method according to the invention a first time point at which a current value for current passing through the consuming device exceeds a first current threshold value and/or a second time point at which the current value drops below a second current threshold value is measured. Then the measured first time point and/or the second time point are compared with each other and/or with other variables to establish plausiblity.
Reliable monitoring of the electrical power or current consuming device results because of the above-described features of the method according to the invention. The method according to the invention reliably monitors the beginning of control, the controlling of the current flow and/or the current, e.g. that flows through a fuel injector device for an internal combustion engine. The method essentially tests whether or not the current flowing through the consuming device is plausible in comparison with the control signal and/or with variables correlated with it.
Preferably the first and the second threshold values take different values. In a simplified embodiment both current threshold values take the same value. The first time point is the time point at which the current that flows through the consuming device exceeds a certain first current value. The second time point is the time point at which the current that flows through the consuming device drops below a second current value.
It is particularly advantageous when the other variables, which are compared with the first and/or second time points, include a control signal that characterizes the start and/or the end of the control process. Preferably the control signal controls a switch means which controls the current flow through the consuming device. Instead of these variables other signals, which depend on the control signal and/or on that which is controlled by the control signal, can be used. For example, the fuel feed signal can be used during the control, which characterizes the start of the fuel injection and/or the end of the fuel injection and/or the fuel injection duration.
In an especially preferred embodiment implausibility is detected when the interval between the first and the second time point is less than a first threshold value and/or greater than a second threshold value. This means that the duration of the time interval during which the current exceeds the threshold value takes an implausible value. Preferably whether or not this time interval is too long and/or too short is tested. First comparison can take place with first values and also with the maximum value and the minimum value for this time interval depending on the size of a variable, which depends on the start of control and the end of the control.
In another embodiment implausibility is detected when the time interval between the first time point and the control signal, which characterizes the beginning of control, is greater than a threshold value. This means that an error is detected when the control signal, which characterizes the end of control is not correlated with an increase of the current beyond the threshold value.
In an additional embodiment implausibility is detected when the time interval between the second time point and the control signal, which characterizes the end of the control signal, is greater than a threshold value. This means that an error is detected when the control signal, which characterizes the end of control is not correlated with a decrease of the current below the threshold value.